1. Field of the Invention
This Invention relates to a camera which can change a photographic range by converting a film size to which an image is photographed to another and, in particular, to a finder optical system for a camera which permits ordinary and panoramic photographies, independently of a photographic optical system.
2. Description of the Related Art
Recently, some of cameras for 35 mm film format have come to be able to trim the upper and lower portions of the image photographed on a film by placing a light-blocking plate adjacent to the upper and lower portions of a film surface within the camera. In this way, the image with a photographic film or print can be made long sideways, and thus panoramic photography that enhances such a wide-screen sensitivity has been popularized.
Most of the finder optical systems for cameras permitting panoramic photography have been designed to use the same field frame, indicative of the photographic range, of a 35 mm full size in the ordinary and panoramic photographies in such a way that frames for ordinary and panoramic photographies overlap the field frame. Specifically, as shown in FIG. 1, a field frame 1 has the marking of a panoramic frame 3, narrowed vertically, indicative of the photographic range for panoramic photography in a frame 2 indicative of the photographic range for ordinary photography. For this reason, when a photographer sees through the finder in the ordinary photography, the panoramic frame 3 overlaps a part of a field image in the frame 2 for ordinary photography. This prevents the recognition of the image of an object to be photographed. For panoramic photography, another image out of the photographic range will be viewed, and hence there is the defect in that the result of the photography is difficult to expect. In either case, since the frames 2 and 3 of two photographic ranges are viewed simultaneously, there is also the defect in that the photographer is liable to confuse the two photographic ranges.
In order to obviate these defects, some of the cameras are also constructed so that a single field frame is employed and its shape varies with the ordinary and panoramic photographies. In this case, however, when the photographic range observable in the panoramic photography is vertically decreased and converted into a shape narrowed to the panoramic frame, the area occupied by the visual field in the finder becomes narrow, with the resultant drawback of giving the photographer the impression that the visual field has diminished.